For high-capacity HTS applications and more particularly very-high-capacity VHTS applications, telecommunications operators wish to have space telecommunications payloads that are sufficiently flexible to meet their needs in terms of:
capacity or capability for allocating passband to the user spots meeting the traffic needs, and
capacity or capability to dynamically adapt the transmission capacity, in terms of quantity or volume of transmission resources, allocated to each user spot according to the variations in traffic demand; and
capacity or capability to rationalize, that is to say minimize, the number of satellite access stations, termed “gateways” and referred to hereinafter as access stations, to meet the instantaneous transmission capacity demanded over the whole set of user spots,
capacity or capability for progressive rollout of the capacity with a minimum of satellite access stations at the start of life while being able to serve the user spots requiring resources; and
capacity or capability to offer the entire band available to each user spot so as to avoid frequency coordination problems; and
capacity or capability to offer links of meshed type making it possible to directly connect certain user spots together at the on-board level (i.e. the payload), that is to say without passing via the ground,
capacity or capability to connect several access stations to one and the same user spot.
Most existing payload architectures, currently proposed or developed in order to allocate transmission capacity to the spots, are based on frequency division of the transmission resources, and typically consist in determining beforehand and forecasting the traffic which might be necessary on each user spot as a function of criteria dependent on economic analyses, of the type among others of population density of the zone covered by the user spot and/or rate of penetration of the terrestrial cellular telecommunications or ground systems, and in best optimizing the architecture of the payload to meet this traffic need defined beforehand. The result obtained by using such an approach typically consists of a static architecture of payload, such as for example that described in FIGS. 1A and 1B, which involves several parameters for adapting the load of each user spot with respect to the final traffic need forecasted, these parameters being defined in terms:
of management of user spots of different diameter, for example fine spots on very capacitive zones and wider spots on less capacitive zones;
of allocation of more or less satellite transmit Tx band per user spot (forward pathway of the transponder in FIG. 1A departing from the access stations connected to the ground network infrastructure, i.e. “forward section” or “Outbound”) and of more or less receive Rx band per user spot (return pathway of the transponder in FIG. 1B arriving at the access stations connected to the ground network infrastructure, i.e. “return section” or “Inbound”); according to FIG. 1A, the transmit band amplified by each high power amplifier HPA on the Tx side of the payload is divided into sub-bands via a frequency demultiplexer (DMUX), for example here a frequency duplexer. According to FIG. 1B and in a symmetric manner, the reception band amplified by each low noise amplifier LNA on the Rx side of the payload is the additional combination of sub-bands via a combiner frequency multiplexer (CMUX), here with two inputs;
of number of access stations GWs, which is defined by the sum of each maximum of transmission capacity that may be necessary for a user spot (and not by the maximal transmission capacity required by the satellite system), this leading to a greater number of access stations than the actually useful need.
It is possible to introduce flexibility into the static architectures described hereinabove by using electromechanical switches and by adding further demultiplexers DMUX and/or multiplexers CMUX. These additional devices afford a little flexibility in selecting the access stations which will serve certain user spots and in selecting the bandwidth allocated to a user spot, but the flexibility remains limited.
Moreover, though the payload architectures obtained by adding these devices can offer a response to meet certain needs requiring limited flexibility, these architectures remain incompatible with the needs defined in terms:
of capacity for each user spot to access the total frequency band of the VHTS or HTS service, each user spot accessing only a fraction of the total band allocated on account of the use of demultiplexers DMUX in satellite transmit Tx and of multiplexers CMUX in satellite receive Rx, and of existence of a simple solution with limited losses which would make it possible to allocate more or less band per user spot or indeed another band;
of an unacceptable over-dimensioning of the whole of the payload architecture if the total band of the VHTS or HTS user service is allocated to each user spot;
of progressive rollout of the services with a minimum of access stations except at the price of a non-negligible complexity of the architecture and a significant impact on the mass of the payload;
of links of “mesh” type, the creation of N2 paths being necessary for a given number N of generated user spots, this being totally unrealistic as regards the global impacts on the payload.